Battle of Okehazama

The Battle of Okehazama (1560) was the first major battle during the rise of Nobunaga Oda, where the 3,000-strong Oda defeated the 25,000-strong Imagawa army led by Yoshimoto Imagawa in a surprise attack. All but two of the senior officers of the Imagawa clan were slain, and the mighty Imagawa were destroyed while their vassal Tokugawa clan was forced to switch allegiance to Nobunaga.

Background
The ambitious Yoshimoto Imagawa gathered an army of 25,000 Imagawa clan troops in preparation for a march on Kyoto, hoping to bring down the Ashikaga Shogunate and become the new Shogun of Japan. However, he had to pass through the lands of the Oda clan, whose daimyo Nobunaga Oda refused to surrender despite only having 3,000 soldiers in his army. The two armies met in battle in the forests of Okehazama on a rainy and foggy day.

The Imagawa army set up a camp in the center of the forest, and Yoshimoto stayed in his red tent. He was so confident in victory that he gave permission for his soldiers to celebrate before the battle, while leaving a few patrols to circle outside of the camp. Nobunaga did not plan on retreating; he decided that he would fool the Imagawa army. He had his men place several banners and hats on a ridge to make it seem as if he had more men, while he prepared to attack the Imagawa before they knew what was happening.

Battle
Nobunaga Oda relied on cavalry for speed and surprise, so he dispatched Oda cavalry to charge the Imagawa patrols. All of the patrols were routed before any of them could report back to camp, leaving the main Imagawa force oblivious to what was occurring outside of the camp. After all four patrols were eliminated, the cavalry returned to the main force, and Nobunaga personally led his forces forwards to attack the Imagawa army. They entered the main camp and captured it in a surprise attack, and Yoshimoto attempted to flee the battlefield. He was stopped in his retreat by Tadakatsu Honda, a sentry and vassal of his ally Ieyasu Tokugawa, who claimed that he would let him through only on Ieyasu's orders. Meanwhile, Nobunaga fought Ieyasu, who swore that he owed his life to Yoshimoto. Once Ieyasu was defeated in the duel, he agreed to serve Nobunaga, and Yoshimoto made his way past Tadakatsu at the same time. Ieyasu and Tadakatsu switched their allegiance, and Yoshimoto's generals fell one-by-one. As he tried to flee, he was beheaded by Oda troops, and his army was massacred.

Aftermath
Nobunaga Oda's victory at Okehazama was an epoch-making moment in Japanese history, as it began his rise to power to become one of the greatest warriors of the land. Ieyasu Tokugawa also had good things in store, as he was now allied with the most-powerful warlord in the land. Hideyoshi Hashiba became Nobunaga's sandal-bearer after the battle, and the two generals Katsuie Shibata and Toshiie Maeda would become great commanders of the Oda clan.